fix playlist export bug
Fix merge issues
Make name more accurate
OK it's all working again
Major cleanup to slider logic
fix bad merge
change all instances of "value" to "parameter"
more notes, fix build
Merge pull request #431 from ywwg/sliderhandler-refector

"no-op" refactor of slider logic into an event handler
Merge pull request #430 from midzer/master

fix playlist export bug
Deere skin: Set TooltipId for Previewdeck controls, Spinny, Coverart. Make Spinny persist="true">
Add source line:number and skin XML line:number to skin warning messages.
Only warn about invalid TooltipId if it is non-empty.
Delete obsolete include directives
New SoundSource/AudioSource API

This is the first step towards a better/cleaner SoundSource API.
The operations for reading audio data have been moved into the
new abstract base class AudioSource.

Currently SoundSource inherits from AudioSource for technical reasons.
This is too much much coupling that needs to be broken up. I have
already some ideas on how to resolve it, but first this work needs to
be integrated.

During the refactoring I've noticed, that the quality and maturity of the
audio decoders for different file types greatly varies:

Good/mature:
- FLAC
- Ogg
- Opus
- WavPack
- libsndfile

Mediocre:
- MP3

Ugly/inefficient:
- M4A
- ModPlug

Untested AudioSource API:
- Apple CoreAudio
- Windows Media Foundation

Unfinished AudioSource API (just a hack):
- FFmpeg

Especially the code for the M4A decoder should be revised and cleaned up as
soon as possible, followed by a review of the MP3 decoder. Reading audio
data must work as stable and efficient as possible. This has priority over
the improvement of the internal software architecture!
Rewrite of the M4A decoder without legacy code
Slightly simplify the analysis of tracks
Initial cleanup of SoundSourceMp3 code
More SoundSourceMp3 optimizations and improvements
Move track metadata properties from SoundSource into separate DTO class